1. Field of the Invention
The present invention relates to a control device for a hybrid vehicle, and in particular relates to a hybrid vehicle that can respond quickly to an assist requirement of a driver at the time of starting the vehicle.
2. Description of the Related Art
Conventionally, a hybrid vehicle provided with an electric motor in addition to a combustion engine serving as a source of drive during the operation of the vehicle is known.
One type of this kind of hybrid vehicle is a parallel hybrid vehicle that uses an electric motor as an auxiliary drive source to assist the output of the combustion engine. This parallel hybrid vehicle carries out various types of control such as, for example, providing auxiliary drive force to the output of the engine by the electric motor during acceleration and charging the battery by deceleration regeneration during deceleration, and maintaining the state of charge of the battery, in order to fulfill the needs of the driver (for example, Japanese Unexamined Patent Application, First Publication, 7-123509).
However, in the above described hybrid vehicle, in the case of requiring an assist depending on the intention of the driver to accelerate the vehicle, an auxiliary drive force may be supplied to the output of the engine by the motor, and the intention of the driver to accelerate the vehicle takes various forms depending on the driving conditions. For example, there is the case in which the driver depresses the accelerator pedal in order to accelerate immediately after the vehicle starts, and the case in which the driver depresses the accelerator pedal during driving in order to accelerate. In particular, in a hybrid vehicle, when the vehicle is stopped, idling is stopped to improve fuel consumption. However, in most cases, each time the engine is stopped due to a traffic signal, the driver depresses the accelerator pedal to accelerate the vehicle after the engine has started.
Therefore, there is the problem that it is impossible to respond to all of the needs of the driver by supplying the assist of the motor by simply determining the need of the assist by the motor from the driver""s intent to accelerate during normal travel.
Thus, the present invention provides a control device for a hybrid vehicle that can accurately respond to the assist request of the driver from the start-up to start of the vehicle.
In order to resolve the above-described problems, the invention described in claim 1 provides a control device for a hybrid vehicle comprising a combustion engine that outputs driving power to the vehicle (for example, engine E in the embodiment), an electric motor for assisting the output of the engine (for example, the motor M in the embodiment), an electric storage device that supplies electric power to this motor (for example, the battery 3 in the embodiment), an output assist determination device that determines appropriateness of assisting the engine output by the motor depending on the driving state of the vehicle (for example, step S004 in the embodiment), a control amount setting device that sets the control amount of the motor depending on the driving state of the engine in the case that a determination is made to carry out assisting of the output of the engine with the motor by the output assist determination device (for example, steps S029, S033, and S034 in the embodiment), an output assist control device that carries out assisting of the output to the engine by the motor based on the control amount set by the control amount setting device (for example, the motor ECU1 in the embodiment), an engine rotation speed detection device (for example, the engine rotation speed sensor S2 in the embodiment) that detects the rotation speed of the engine (for example, the engine rotation speed NE in the embodiment), and an after-start-up output assist permission device that permits an assist of the engine output by the motor when the engine rotation speed detection device has detected that the engine rotation speed has exceeded a predetermined rotation speed during the engine start-up (for example, step S005 in the embodiment), wherein the assist of the engine output by the motor is carried out by the output assist control device when the output assist is permitted by the after-start-up output assist permission device.
By constituting the control device for the hybrid vehicle in this manner, at the time of cranking by the electric motor during start-up, for example, when the engine rotation speed detecting device has determined that the engine rotation speed exceeds the rotation speed that provides the torque that allows the engine to rotate and then drive under its own power after the engine start-up operation, in the case that the output assist determination device has determined that the driver has the intention of accelerating, the after-start-up output assist permission device permits applying an assist drive to the engine from the motor.
A second aspect of the invention is that a predetermined engine rotation speed is the rotation speed that provides the engine to rotate and then drive under its own power after the engine start-up operation (for example, the predetermined value #TMOTST in the embodiment).
By constituting the control device of the hybrid vehicle as described above, the engine can be converted quickly to self-powered movement.